BURLINGTON, Vermont There they come trudging along, straight upright on stubby legs, shoulders swinging back and forth with each step, coming into focus on the screen just as I'm eating my first bite of popcorn. Then Morgan Freeman's otherworldly voice informs us that these beings are on a long and difficult journey in one of the most inhospitable places on earth, and that they are driven by their "quest for love."

I've long known the story of the emperor penguins, but to see the sheer beauty and wonder of it all come into focus in "March of the Penguins," the sleeper summer hit, still took my breath away. As the movie continues, everything about these animals seems on the surface utterly different from human existence; and yet at the same time the closer one looks the more everything also seems familiar.

Stepping back and viewing from the context of the vast diversity of millions of other organisms that evolved on the tree of life - grass, trees, tapeworms, hornets, jellyfish, tuna, green anoles and elephants - these animals marching across the screen are practically kissing cousins to us.

I admired the heroics of both the birds and the intrepid camera crew that braved the inhumanly hostile environments of the Antarctic. But as a research biologist, I also admired the boldness of the filmmaker, Luc Jacquet, to face down the demon of anthropomorphizing his subjects.

Which brings me back to Freeman's use of the word "love." The unspoken rule is that the word is to be applied only to one creature on earth, homo sapiens. But why?

A look at the larger picture shows this presumption of exclusivity is utterly unproved. In a broad physiological sense, we are practically identical not only with other mammals but also with birds - muscle for muscle, eye for eye, nerve for nerve, lung for lung, brain for brain, hormone for hormone - except for differences in detail of particular design specifications.

Functionally, I suspect love is an often temporary chemical imbalance of the brain induced by sensory stimuli that causes us to focus on something that carries an adaptive agenda. Love is an adaptive feeling or emotion - like hate, jealousy, hunger, thirst - necessary where rationality alone would not suffice to carry the day.

Could rationality alone induce a penguin to trek 70 miles over the ice in order to mate and then balance an egg on his toes while fasting for four months in total darkness and enduring wind-driven temperatures of minus-80 degrees Fahrenheit?

Even humans require an overpowering love to do the remarkable things that parents do for their children. The penguins' drives to persist in proximally bizarre behavior in the face of what must otherwise be overpowering temptations to do otherwise also suggests that they love to an inordinate degree. Where they differ from us is that they can "love" an egg as much or more than a peeping fuzz-ball of a hatchling.

In the last half-century, the hidden reality of nature has been revealed as never before. Our general perceptions, though generally lagging behind, are now catching up. We are becoming weaned from the make-believe world of Walt Disney's "Bambi."

Is that why high-tech documentaries like "Microcosmos," "Winged Migration," "March of the Penguins" and, in a slightly different vein, Werner Herzog's new "Grizzly Man" are catching on?

I suspect that the new breed of nature film will become increasingly mainstream because, as we learn more about ourselves from other animals and find out that we are more like them than supposed, we are now allowed to "relate" to them, and therefore to empathize.

Nature is the greatest show on earth, and reverence for life requires acknowledging the differences between ourselves and the animals as well as seeing our relatedness.

If we gain more exposure to the real - and if the producers and studios invest half as much care and expense into portraying animals as they do into showing ourselves - I suspect the results will be as profitable, in economic as well as emotional and intellectual terms - as the "March of the Penguins."

(Bernd Heinrich, emeritus professor at the University of Vermont, is the author of ''The Geese of Beaver Bog.'')